EP1466420B1 - Verbesserte zeitnachführschleife - Google Patents

Verbesserte zeitnachführschleife Download PDF

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Publication number
EP1466420B1
EP1466420B1 EP02720819A EP02720819A EP1466420B1 EP 1466420 B1 EP1466420 B1 EP 1466420B1 EP 02720819 A EP02720819 A EP 02720819A EP 02720819 A EP02720819 A EP 02720819A EP 1466420 B1 EP1466420 B1 EP 1466420B1
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European Patent Office
Prior art keywords
signal
timing
overlapping
accumulations
communication signal
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French (fr)
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EP1466420A1 (de
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Luca Blessent
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Qualcomm Inc
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Qualcomm Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7085—Synchronisation aspects using a code tracking loop, e.g. a delay-locked loop

Definitions

  • the invention relates to communications. More particularly, the invention relates to a novel and improved method and apparatus for synchronizing a communication signal timing with a timing of a receiver that receives the communication signal.
  • CDMA modulation is one of several techniques for facilitating communications in which a large number of system users are present. Although other techniques such as time division multiple access (TDMA), frequency division multiple access (FDMA), and AM modulation schemes such as amplitude companded single sideband (ACSSB) are known, CDMA has significant advantages over these other techniques.
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • AM modulation schemes such as amplitude companded single sideband (ACSSB)
  • CDMA modulation allows a large number of mobile telephone system users, each having a transceiver, to communicate through satellite repeaters or terrestrial base stations (also known as cell-site stations, or cell-sites) using CDMA spread spectrum communication signals.
  • the frequency spectrum can be reused multiple times, thus permitting an increase in system user capacity.
  • the signal from each user may be multiplied by a distinct signature waveform before transmission.
  • the signature waveform is a signal which has a much larger bandwidth than the information bearing signal from the user.
  • the transmitted signal is thus a spread spectrum signal
  • CDMA is a spread spectrum technology. All users use different signature waveforms to expand their signal bandwidth. As a result, the use of CDMA may result in a much higher spectral efficiency than can be achieved using other multiple access techniques.
  • a mobile receiver in a portable communication system operates in an environment that subjects the receive signal to numerous degradations.
  • the signal transmitted from a signal source is subject to numerous conditions, such as attenuation, interference, scattering, and reflections, prior to arrival at a receiver.
  • the receiver must be able to recover the signal in spite of all these degradations, in order for a successful communication link to be established.
  • Structures such as buildings and surrounding terrain, including walls and hillsides, contribute to the scattering and reflection of the transmitted signal.
  • the scattering and reflection of the transmitted signal may result in multiple signal paths from the transmitter to the receiver. The contributors to the multiple signal paths change as the receiver moves.
  • the signal timing In order to accurately decode a signal from a CDMA mobile unit the signal timing must be synchronized with the base station timing. As the mobile unit moves further away from the base station the signal takes an increasingly long period of time to reach the base station and if no timing adjustments are implemented at the base station an incoherent or attenuated signal will be received. In addition, if the weather conditions change so as to increase the signal attenuation, the timing of the incoming signal may be further displaced from the timing expected at the base station.
  • a Time Tracking Loop is commonly used to acquire and track the timing of a signal received at the base station in order to synchronize the base station timing with the received signal timing.
  • the TTL may be used to refine the estimate and to track dynamic variations of the offset due to code doppler, pseudo-noise ("PN") slewing, or other effects.
  • PN pseudo-noise
  • a TTL comprises two synchronization phases, namely, an acquisition phase and a tracking phase. During the acquisition phase the TTL needs to rapidly correct for the initial timing error. Subsequently, after the TTL converges to a timing estimate that is reasonably close to the received signal timing reference, the acquisition phase ends and the tracking phase begins.
  • the TTL follows slow variations of the timing of the received signal.
  • the faster the acquisition phase the higher the standard deviation of the residual timing error in the tracking phase.
  • a signal received by a TTL that has a shortened acquisition phase will have an increased standard deviation during the tracking phase.
  • a TTL commonly operates by measuring an energy or magnitude difference in an early signal sample and a late signal sample. This difference may then be used to determine if the base station timing should be adjusted forward or backwards. For example, if the late signal sample has a higher energy than the early signal sample, the base station timing should be adjusted forward, closer to the higher energy signal. This process, however, may require a considerable length of time to accurately lock on to the signal timing. This problem may be decreased somewhat through the process of accumulating signal samples over disjoint time intervals before adjusting the base station timing. However, in low SNR situations use of this method may not sufficiently decrease the signal acquisition phase. Furthermore, even if the signal acquisition phase is decreased, the standard deviation of the timing error will likely increase, according to general principles of TTL's.
  • US-A-6 141 372 which describes a system for digitally downconverting and despreading a multi-channel analog direct sequence spread spectrum signal.
  • the system includes a free-running, non-steering, clock generator which outputs an A/D sample clock, and an A/D sample clock having a rate which is an integral multiple of a chip rate of the spread spectrum signal.
  • An A/D converter which receives the spread spectrum signal and the A/D sample clock and outputs a digitized multi-channel signal from the multi-channel spread spectrum signal, and a local pseudo-noise sequence signal source which outputs M local pseudo-noises, wherein M is an integer greater that 1 is also included.
  • a multi-channel complex downconverter/polyphase filter which receives the digitized multi-channel signal and the A/D sample clock and a sample timing phase control signals, simultaneously filters and downconverts the digitized multi-channel signal to baseband, corrects timing phase misalignment between the digitized multi-channel signal and the locally generated pseudo-noise sequences, and outputs a multi-channel complex corrected baseband signal is provided.
  • a TTL coupled to a signal receiver uses overlapping sample accumulations in order to acquire and track a received spread spectrum signal with increased speed and accuracy.
  • sample accumulations are formed by grouping together a predetermined number of consecutive samples. Sample accumulations are groups of samples. Overlapping sample accumulations may be created by overlapping a predetermined portion of adjacent sample accumulations. In one embodiment, 50% of adjacent sample accumulations are overlapped such that the latter half (50%) of a first sample accumulation is overlapped by the first half (50%) of a second sample accumulation. Other predetermined portions of adjacent sample accumulations, such as 25% or 75%, may be overlapped also. After the overlapping sample accumulations are created they are transmitted to the TTL in order to determine a timing error indicative of the difference between the timing of the received spread spectrum signal and the signal receiver timing.
  • the TTL includes a timing discriminator which creates an early overlapping accumulation signal and a late overlapping accumulation signal.
  • an early and late signal are created by a psuedo-noise despreader using advanced and delayed pseudo-noise offsets. Subsequently, early and late overlapping signal accumulations are created using the early and late signals, respectively.
  • the TTL compares the early and late overlapping accumulation signals in order to determine an updated timing error.
  • the receiver timing is thereafter periodically adjusted according to the timing error determined by the TTL.
  • a system using overlapping accumulations may provide a similar standard deviation of a tracking error in a tracking phase as a system using disjoint accumulations having a longer acquisition phase.
  • the use of overlapping accumulations may provide a decreased standard deviation of tracking error in the tracking phase when the length of the acquisition phases are the same.
  • Figure 1 illustrates an exemplary communication system which utilizes CDMA modulation techniques in communications between mobile users and cell-sites.
  • Figure 2 is a functional block diagram illustrating a timing error signal generator.
  • Figure 3 is a block diagram illustrating an improved method of synchronizing the receiver timing with the mobile unit timing.
  • FIG. 4 is a block diagram illustrating the functional components of a TTL.
  • Figure 5 is a graph illustrating a comparison of the standard deviation of residual timing error for a TTL using 50% overlapped accumulations and a TTL using disjoint accumulations.
  • the invention will be disclosed with reference to an exemplary CDMA wireless communication system operating in accordance with the principles outlined in the CDMA2000 standard.
  • inventive principles described herein are equally applicable to other wireless communication systems that employ spread spectrum signals.
  • a the invention is applicable to systems using a punctured or discontinuous pilot channel.
  • Various embodiments of the invention are equally applicable to the wideband CDMA (W-CDMA) standard(s), as well as many of the other proposed 3G communication standards.
  • W-CDMA wideband CDMA
  • bits or “bits” as used herein is often used alongside the term “chip” or “chips”. It will be understood by one of ordinary skill in the art that “bit” refers to a unit of information, whereas “chip” refers to a unit of the spreading code used in a CDMA system. However, the use of the term “chip” herein is merely for accuracy in explanation and is not intended to limit the invention to CDMA systems. The invention is equally applicable to systems that do not spread "bits" of information with "chips" of a spreading code.
  • Figure 1 illustrates an exemplary communication system which utilizes CDMA modulation techniques in communications between the mobile users 16, and the cell-sites 12.
  • Cellular systems in large cities may have hundreds of cell-site stations 12 serving hundreds of thousands of mobile telephones 16.
  • the use of CDMA techniques readily facilitates increases in user capacity as compared to conventional FM modulation cellular systems.
  • a system controller 10 typically includes a switch and appropriate interface and processing hardware for providing system control information to the cell-sites. Controller 10 controls the routing of telephone calls from the public switched telephone network (PSTN) to the appropriate cell-site for transmission to the appropriate mobile unit. Controller 10 also controls the routing of calls from the mobile units via at least one cell-site to the PSTN. Controller 10 may direct calls between mobile users via the appropriate cell-site stations since such mobile units do not typically communicate directly with one another.
  • PSTN public switched telephone network
  • Controller 10 may be coupled to the cell-sites by various means such as dedicated telephone lines, optical fiber links or by radio frequency communications.
  • FIG 1 two exemplary cell-sites, 12A and 12B, are illustrated, along with two exemplary mobile units 16a and 16b which include cellular telephones.
  • Arrows 20a-20b and 22a-22b respectively define the possible communication links between cell-site 12A and mobile units 16.
  • arrows 24a-24b and arrows 26a-26b respectively define the possible communication links between cell-site 12B and mobile units 16.
  • Cell-sites 12 normally transmit using equal power.
  • Cell-sites 12 in the typical case, are terrestrial base stations which define cell service areas.
  • earth orbit relay satellites such as satellites 13 may be used to provide more complete cellular coverage, particularly for remote areas.
  • signals may be relayed between the mobile users and the terrestrial base stations using satellites 13.
  • the satellite case also provides the ability for communication between a mobile unit and one or more base stations via multiple transponders on the same satellite 13 or through different satellites 13.
  • Mobile unit 16a measures the total received power in pilot signals transmitted by cell-sites 12 upon paths 20a and 26a.
  • mobile unit 16b measures the total received power in pilot signal as transmitted by cell-sites 12 upon paths 22a and 24a.
  • pilot signal power is measured in the receiver where the signal is a wideband signal. Accordingly, this power measurement is made prior to correlation of the received signal with a PN spectrum spreading signal.
  • the received signal power When mobile unit 16a is closer to cell-site 12A, the received signal power will be dominated by the signal traveling path 20a. When mobile unit 16a is nearer to cell-site 12B, the received power will be dominated by the signal traveling on path 26a. Similarly, when mobile unit 16b is closer to cell-site 12B, the received power will be dominated by the signal on path 24a. When mobile unit 16b is closer to cell-site 12A, the received power will be dominated by the signal traveling on path 22a.
  • Each of mobile units 16 uses the resultant measurement, together with knowledge of the cell-site transmitter power and the mobile unit antenna gain to estimate the path loss to the closest cell-site.
  • the estimated path loss, together with knowledge of the mobile antenna gain and the cell-site G/T may be used to determine the nominal transmitter power required to obtain the desired carrier-to-noise ratio in the cell-site receiver.
  • the determination of the nominal transmitter power may be accomplished according to various different equations and is generally well known in the communication art.
  • the knowledge by the mobile units of the cell-site parameters may be either fixed in memory or transmitted in cell-site information broadcast signals to indicate other than nominal conditions for a particular cell-site.
  • FIG. 2 a functional block diagram of a timing error signal generator is illustrated.
  • input RAM 202 stores samples of the received waveform and provides them to a despreader 206 where they are despread using a PN code generated by PN generator 204.
  • PN generator 204 The process of generating a PN code and despreading a CDMA signal is well known in the communication art, and, thus, will not be discussed herein.
  • Sampler 208 performs a periodic sampling of the despread signal from the despreader 206.
  • the input to timing discriminator 450 is a despread signal with a timing error ⁇ e defining the difference in the received signal timing and the receiver timing.
  • Despreader 206 outputs a signal s( ⁇ ), which is then received by an advance module 210 and a retard module 211, which are used to create respective early and late signals.
  • the early signal comprises a sequence of despread chips that were despread with advanced PN offset while the late pilot signal comprises a sequence of despread chips that were despread with a delayed PN offset.
  • the PN offset is one-half chip such that the early signal is one-half chip earlier and the late signal is one-half chip later than the received signal s( ⁇ ).
  • the early signal 220 and late signal 224 are respectively presented to accumulators 212A and 212B where overlapping accumulations are formed over a predetermined number of samples.
  • the number of samples in an accumulation, or sample group is implementation dependent and therefore an accumulation may comprise any number of samples. For example, one embodiment may use 64 samples per accumulation, while another embodiment may use 256 samples per accumulation.
  • overlapping the accumulations of samples By overlapping the accumulations of samples, adjustments to the system timing may be made more rapidly than if disjoint samples are used.
  • a system using overlapping accumulations may provide a similar standard deviation of the tracking error in a tracking phase as a system using disjoint accumulations having a longer acquisition phase.
  • the use of overlapping accumulations may provide a decreased standard deviation of tracking error in the tracking phase when the length of the acquisition phases are the same.
  • the accumulated symbols output from accumulators 212A and 212B are then respectively input to energy calculators 214A and 214B.
  • Energy calculators 214A and 214B calculate the energy contained in the accumulated symbols of the early and late pilots. For example, if the early and late pilots are QPSK-encoded, the energy calculators 214A, 214B calculate the energy using the relationship I 2 + Q 2 , where I and Q are the in-phase and quadrature phase components of the signals, respectively.
  • energy calculators 214 calculate the magnitude of the energy, i.e ., the square root of the energy calculations, contained in the early and late symbols. In addition, the calculation of magnitude may be approximated so that no significant delay is introduced by the energy calculators 214.
  • the difference between the energy in the early pilot and the late pilot is then calculated by subtractor 216 to generate a value indicative of the time tracking error of the PN generator 204 for the received signal.
  • the resultant difference value output by subtractor 216 is filtered by filter 218 and provided as a time error signal for further use by other circuitry, such as adjustment of the PN generator timing, for example.
  • Filter 218 may include an accumulator and/or other processing circuitry for smoothing the instantaneous variation in the time error signal.
  • FIG. 3 is a block diagram illustrating an improved method of synchronizing the timing of a receiver, e.g ., the base station, with the timing of a mobile unit.
  • a receiver e.g ., the base station
  • the time tracking loop of many existing communication systems adjusts the system timing according to an accumulation of disjoint signals over a period of time.
  • this method may require a significant amount of time to effectuate a timing adjustment.
  • the illustrated method in Figure 3 may significantly reduce the length of the acquisition phase of a TTL without increasing the standard deviation of the timing error in the subsequent tracking phase.
  • the base station receives a CDMA signal from a mobile unit 16.
  • the CDMA signal comprises a stream of data blocks that are typically encoded with voice data.
  • step 320 samples of the incoming signal are taken at a rate greater than the chip rate of the system.
  • a typical CDMA communication system has a chip rate R of 1.2288 MHz, thus transmitting 1.2288 Million chips per second. Therefore, if samples are taken at a rate of 2.4576 MHz, two samples will be taken during each chip time. If samples are taken at a rate of N x R, N samples will be taken during each chip time T. In an advantageous embodiment, samples are taken at a rate of 2 x R, thus sampling each chip twice. The samples may then be interpolated by a factor of M to further increase the number of samples available.
  • step 330 samples are overlapped by the overlapping percentage P before entering the time tracking loop ("TTL").
  • TTL time tracking loop
  • P 50%
  • the latter half (50%) of a first accumulation will be overlapped by the first half (50%) of a second accumulation.
  • the use of overlapping accumulations may provide a similar standard deviation of the tracking error in a tracking phase as in a system using disjoint accumulation with a longer acquisition phase.
  • the use of overlapping accumulations may provide a decreased standard deviation of tracking error in the tracking phase when the length of the acquisition phases are the same.
  • the acquisition phase may decrease the tracking error more quickly than in a system with a slower update rate, e.g ., a system using disjoint accumulations.
  • step 340 the overlapped accumulations are used by a timing discriminator 450 ( Figure 2 ) to generate a timing estimate, as discussed with reference to Figure 2 , which is used to synchronize the base station and the received signal timing.
  • FIG. 4 is a block diagram illustrating the functional components of a TTL.
  • the TTL 400 performs both the acquisition and tracking of the received signal timing.
  • the TTL 400 system is driven by a stream of accumulated overlapping samples 410 having a timing error of ⁇ , indicating the difference between the received signal timing and the receiver timing.
  • the overlapping accumulations are represented in the figures as s( ⁇ ). In general, overlapping of accumulations is accomplished by overlapping a portion P of a current sample accumulation starting at time t with a sample accumulation stored in the buffer that started at time t-1. The overlapping of accumulations is discussed above with reference to Figure 3 .
  • the timing adjust module 420 performs the adjustment of the received signal timing according to the timing estimate ⁇ ' received from loop filter 440.
  • the timing of the received signal is delayed by the timing adjust module 420 in order to output a time adjusted signal 430 that approaches synchronization with the receiver timing.
  • the PN generator 204 timing is offset by an amount based on ⁇ ' so that the PN code is properly aligned with the received signal.
  • s( ⁇ e ) drives the TTL through the timing discriminator 450, for use in updating the timing estimate ⁇ '.
  • the timing discriminator 450 generates a new timing estimate ⁇ ' based on a comparison of early and late accumulations (see Figure 2 ), which is filtered by loop filter 440 and transmitted back to the timing adjust module 420.
  • the timing estimate ⁇ ' converges towards ⁇ as ⁇ ' is updated in relatively large amounts.
  • the timing estimate ⁇ and the timing error ⁇ have become sufficiently close (i.e., ⁇ e approaches zero) the acquisition phase ends and the tracking phase begins.
  • the tracking phase slow variations of ⁇ are tracked keeping ⁇ e to a desirable small value.
  • Figure 5 is a graph illustrating a comparison of the standard deviation of residual timing error ⁇ e for a TTL using 50% overlapped accumulations, i . e . 50% overlapped sample groups, and a TTL using disjoint accumulations ( i . e ., 0% overlap).
  • the overlapping percentage P may be adjusted by the TTL system design to any percentage and is not limited to the examples discussed herein.
  • Curve 710 illustrates the standard deviation of a TTL system using 50% overlapped accumulations in calculating a timing error.
  • P the standard deviation of a TTL system using disjoint accumulations
  • P 0%
  • the 64 samples of each accumulation are followed by each subsequent accumulation, but no overlapping of samples occurs.
  • the use of overlapping accumulations may decrease the standard deviation of the residual timing error ⁇ e compared to TTL's using disjoint sample accumulations.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • a general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.
  • a processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
  • a software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
  • An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium.
  • the storage medium may be integral to the processor.
  • the processor and the storage medium may reside in an ASIC.
  • the ASIC may reside in a mobile station, base station, or base station controller.
  • the processor and the storage medium may reside as discrete components in a mobile station, base station, or base station controller.

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Claims (29)

  1. Ein Verfahren zum Nachführen bzw. Verfolgen eines empfangenen Kommunikationssignals, wobei das Verfahren aufweist:
    Akkumulieren (330) einer Vielzahl von Abtastungen bzw. Abtastwerten von dem empfangenen Kommunikationssignal, um eine Vielzahl von Abtastgruppen zu bilden, wobei jede von den Abtastgruppen eine vorbestimmte Anzahl von Abtastungen aufweist;
    Überlappen (330) vorbestimmter Abschnitte von benachbarten Abtastgruppen; und
    Bestimmen (340) eines Timing- bzw. Zeitsteuerungsfehlers basierend auf den überlappten Abtastgruppen.
  2. Verfahren nach Anspruch 1, wobei das empfangene Kommunikationssignal ein CDMA Reverse- bzw. Rückwärtsverbindungspilotsignal ist.
  3. Ein Verfahren zum Verringern der Standardabweichung von einem Resttimingfehler in einer Zeitnachführschleife (400), das Verfahren nach Anspruch 1 aufweisend, und wobei das Verfahren ferner aufweist:
    periodisches Abtasten (320) des empfangenen Kommunikationssignals zum Erzeugen der Vielzahl von Abtastungen bzw. Abtastwerten;
    Speichern (330) wenigstens einiger der Abtastungen in einem Speicher um eine Vielzahl von Akkumulationen entsprechend der Vielzahl von Abtastgruppen zu bilden, wobei jede Akkumulation K Abtastungen aufweist;
    wobei das Überlappen (330) Überlappen benachbarter Akkumulationen in dem Speicher um einen Überlappungsfaktor P aufweist;
    Bestimmen (340) einer Timing-Anpassung basierend auf den Überlappungs-Akkumulationen; und
    Einstellen bzw. Anpassen (340) von einem Timing von dem empfangenen Kommunikationssignal gemäß der Timing-Anpassung.
  4. Verfahren nach Anspruch 3, wobei das Kommunikationssignal ein Spreizspektrum-Kommunikationssignal ist.
  5. Verfahren nach Anspruch 4, wobei das Kommunikationssignal ein CDMA Reverse- bzw. Rückwärtsverbindungspilotsignal ist.
  6. Verfahren nach Anspruch 3, wobei K in dem Bereich von ungefähr 32 bis 512 ist.
  7. Verfahren nach Anspruch 3, wobei P in dem Bereich von 25 % bis 75 % ist.
  8. Verfahren nach Anspruch 7, wobei P ungefähr 50 % ist.
  9. Verfahren nach Anspruch 8, das ferner aufweist:
    Kreieren eines early bzw. frühen Überlappungsakkumulationssignals, das ein Timing von ungefähr einem halben Chip früher als das empfangene Kommunikationssignal besitzt; und
    Kreieren eines late bzw. späten Überlappungsakkumulationssignals, das ein Timing von ungefähr einem halben Chip später als das empfangene Kommunikationssignal besitzt.
  10. Verfahren nach Anspruch 9, wobei der Akt des Bestimmens aufweist:
    Vergleichen der Energie von dem frühen Überlappungsakkumulationssignal und dem späten Überlappungsakkumulationssignal um die Timing-Einstellung bzw. -Anpassung zu bestimmen.
  11. Verfahren nach Anspruch 9, wobei der Akt des Bestimmens aufweist:
    Vergleichen der Größe von dem frühen Überlappungsakkumulationssignal und dem späten Überlappungsakkumulationssignal um die Timing-Einstellung zu bestimmen.
  12. Ein System (400) zum Nachführen bzw. Verfolgen eines empfangenen Kommunikationssignals, wobei das System aufweist:
    einen Akkumulator konfiguriert zum Bilden einer Vielzahl von Akkumulationen (410) von einer vorbestimmten Anzahl von Signaltastungen bzw. -abtastungen, wobei der Akkumulator benachbarte Akkumulationen kombiniert, so dass vorbestimmte Abschnitte von benachbarten Akkumulationen überlappt werden; und
    einen Timing- bzw. Zeitsteuerungsdiskriminator (450) konfiguriert zum Bestimmen eines Timing-Fehlers basierend auf den überlappten Akkumulationen (410).
  13. System nach Anspruch 12, wobei das empfangene Kommunikationssignal ein Spreizspektrumsignal ist, wobei das System ferner aufweist:
    einen Entspreizer (206) konfiguriert zum Entspreizen des empfangenen Kommunikationssignals unter Verwendung eines Pseudo-Rauschversatzes, assoziiert mit dem Timing-Fehler.
  14. Ein System zum Nachführen eines Timing-Fehlers in einem Spreizspektrum-Kommunikationssystem, dass das System nach Anspruch 12 aufweist, wobei der Timing-Fehler eine Differenz zwischen einer Timing-Charakteristik von dem empfangenen Kommunikationssignal und einem Timing-Indikator von einer Empfangseinheit ist, wobei das System ferner aufweist:
    Mittel (208) zum Abtasten des empfangenen Kommunikationssignals, um eine Vielzahl von Abtastungen bzw. Abtastwerten zu erzeugen;
    Mittel zum Speichern von wenigstens einigen von den Abtastungen in einem Speicher um eine Vielzahl von Akkumulationen zu bilden, wobei jede Akkumulation die vorbestimmte Anzahl von Tastungen aufweist;
    Mittel (212) zum Überlappen von vorbestimmten Abschnitten von benachbarten Akkumulationen um eine Vielzahl von überlappenden Akkumulationen zu bilden; und
    Mittel (214, 216, 218) zum Bestimmen des Timing-Fehlers basierend auf den überlappenden Akkumulationen.
  15. System nach Anspruch 14, wobei das empfangene Kommunikationssignal ein CDMA Signal ist.
  16. System nach Anspruch 14, wobei der vorbestimmte Abschnitt ungefähr fünfzig Prozent (50 %) ist.
  17. System nach Anspruch 14, wobei jede Akkumulation eine vorbestimmte Anzahl von aufeinanderfolgenden Abtastungen aufweist.
  18. System nach Anspruch 12, das einen Signalprozessor aufweist zum Empfangen des Spreizspektrum-Kommunikationssignals, einen Timing-Mechanismus besitzend, der um den Timing-Fehler versetzt ist, wobei der Signalprozessor aufweist:
    ein Abtastmodul (208), konfiguriert zum Abtasten des empfangenen Kommunikationssignals, und zum Kreieren der Vielzahl von Abtastakkumulationen, wobei jede von den Abtastakkumulationen die vorbestimmte Anzahl von Abtastungen aufweist, wobei vorbestimmte Abschnitte von benachbarten Abtastakkumulationen überlappt sind;
    ein Beschleunigungsmodul (210), konfiguriert zum Erzeugen eines frühen bzw. early Kommunikationssignals, abgeleitet von der Vielzahl von überlappenden Akkumulationen;
    ein Verzögerungsmodul (211) konfiguriert zum Erzeugen eines späten bzw. late Kommunikationssignals, abgeleitet von der Vielzahl von überlappenden Akkumulationen; und
    einen Timing-Diskriminator (214, 216, 218) konfiguriert zum Messen der Energie-Differenz zwischen den frühen und späten Kommunikationssignalen und ansprechend darauf, Bestimmen eines Timing-Fehlers.
  19. Signalprozessor nach Anspruch 18, wobei der Timing-Fehler genutzt wird zum Versetzen von dem Timing-Mechanismus.
  20. Signalprozessor nach Anspruch 18, wobei das frühe Kommunikationssignal ungefähr eine halben Chip früher als das empfangene Kommunikationssignal ist.
  21. Signalprozessor nach Anspruch 18, wobei das späte Kommunikationssignal ungefähr eine halben Chip später als das empfangene Kommunikationssignal ist.
  22. Signalprozessor nach Anspruch 18, wobei das empfangene Kommunikationssignal ein CDMA Signal ist.
  23. Signalprozessor nach Anspruch 18, wobei das empfangene Kommunikationssignal ein CDMA 2000 Rückwärtsverbindungs- bzw. Reverse-Pilotsignal ist.
  24. System nach Anspruch 12, das einen Signalprozessor aufweist, der einen Timing-Mechanismus besitzt, der um den Timing-Fehler versetzt ist, wobei der Signalprozessor aufweist:
    einen Abtaster (208), konfiguriert zum Erlangen einer Vielzahl von Abtastungen von dem empfangenen Kommunikationssignal;
    einen Akkumulator konfiguriert zum Kreieren einer Vielzahl von Abtastgruppen entsprechend der Vielzahl von Akkumulationen, die die vorbestimmte Anzahl von der Vielzahl von Tastungen aufweisen, wobei der Akkumulator vorbestimmte Abschnitte von benachbarten Abtastgruppen überlappt, um ein On-Time- bzw. pünktliches Signal zu bilden, das eine Vielzahl von überlappenden Abtastgruppen aufweist;
    ein Beschleunigungsmodul (210), konfiguriert zum Kreieren eines frühen bzw. voreilenden Signals, abgeleitet von der Vielzahl von überlappenden Abtastgruppen;
    ein Verzögerungsmodul (211), konfiguriert zum Kreieren eines späten bzw. nacheilenden Signals, abgeleitet von der Vielzahl von überlappenden Abtastgruppen; und
    einen Timing-Diskriminator (214, 216, 218) konfiguriert zum Messen der Energie-Differenz zwischen den frühen und späten Kommunikationssignalen und, ansprechend darauf, Bestimmen eines Timing-Fehlers.
  25. Signalprozessor nach Anspruch 24, wobei der Timing-Fehler genutzt wird zum Versetzen von dem Timing-Mechanismus.
  26. Signalprozessor nach Anspruch 24, wobei das frühe Kommunikationssignal weniger als ein Chip vor dem pünktlichen Signal ist, und das späte Kommunikationssignal weniger als ein Chip nach dem pünktlichen Signal ist.
  27. Signalprozessor nach Anspruch 24, wobei das Kommunikationssignal ein Spreizspektrumssignal ist.
  28. Signalprozessor nach Anspruch 24, wobei die vorbestimmte Zahl in dem Bereich von ungefähr 32 bis 512 ist.
  29. Signalprozessor nach Anspruch 24, wobei die vorbestimmte Zahl in dem Bereich von ungefähr 32 bis 512 ist.
EP02720819A 2002-01-18 2002-01-18 Verbesserte zeitnachführschleife Expired - Lifetime EP1466420B1 (de)

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US20070213067A1 (en) * 2006-03-09 2007-09-13 Patrick Li Wireless communication handoffs within a macrocell

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CA2473610C (en) 2010-11-23
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